88
terminal EAC−1 is energized with 115 vac when the
blower motor BLWM is operating.
When the thermostat is satisfied, the R−to−G−and−Y cir-
cuits are opened. The outdoor unit will stop, and the fur-
nace blower motor BLWM will continue operating at cool-
ing airflow for an additional 90 sec. Jumper Y/Y2 to
DHUM to reduce the cooling off−delay to 5 sec. See Fig.
38.
b. Single−Stage Thermostat and Two−Speed Cooling
(Adaptive Mode) −
See Fig. 38 and 39 for thermostat connections.
This furnace can operate a two−speed cooling unit with a
single−stage thermostat because the furnace control CPU
includes a programmed adaptive sequence of controlled
operation, which selects low−cooling or high−cooling op-
eration. This selection is based upon the stored history of
the length of previous cooling period of the single−stage
thermostat.
NOTE: The air conditioning relay disable jumper ACRDJ must
be connected to enable the adaptive cooling mode in response to a
call for cooling. See Fig. 38. When ACRDJ is in place the furnace
control CPU can turn on the air conditioning relay ACR to
energize the Y/Y2 terminal and switch the outdoor unit to
high−cooling.
The furnace control CPU can start up the cooling unit in either
low− or high−cooling. If starting up in low−cooling, the furnace
control CPU determines the low−cooling on−time (from 0 to 20
minutes) which is permitted before switching to high−cooling. If
the power is interrupted, the stored history is erased and the furnace
control CPU will select low−cooling for up to 20 minutes and then
energize the air conditioning relay ACR to energize the Y/Y2
terminal and switch the outdoor unit to high−cooling, as long as
the thermostat continues to call for cooling. Subsequent selection is
based on stored history of the thermostat cycle times.
The wall thermostat “calls for cooling”, closing the
R−to−G−and−Y circuits. The R−to−Y1 circuit starts the outdoor
unit on low−
cooling speed, and the R−to−G−and−Y1 circuits starts
the furnace blower motor BLWM at low−cooling airflow which is
the true on−board CF selection as shown in Fig. 38.
If the furnace control CPU switches from low−cooling to
high−cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay ACR is
energized the R−to−Y1−and−Y2 circuits switch the outdoor unit to
high−cooling speed, and the R−to−G−and−Y1−and−Y/Y2 circuits
transition the furnace blower motor BLWM to high−cooling
airflow. High−cooling airflow is based on the A/C selection shown
in Fig. 38.
NOTE: When transitioning from low−cooling to high−cooling the
outdoor unit compressor will shut down for 1 minute while the
furnace blower motor BLWM transitions to run at high−cooling
airflow.
The electronic air cleaner terminal EAC−1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R−to−G−and−Y circuit are
opened. The outdoor unit stops, and the furnace blower BLWM
and electronic air cleaner terminal EAC−1 will remain energized
for an additional 90 sec. Jumper Y1 to DHUM to reduce the
cooling off−delay to 5 sec. See Fig. 38.
c. Two−Stage Thermostat and Two−Speed Cooling
See Fig. 38 and 39 for thermostat connections
NOTE: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. See Fig. 38.
The thermostat closes the R−to−G
−and−Y1 circuits for
low−cooling or closes the R−to−G−and−Y1−and−Y2 circuits for
high−cooling. The R−to−Y1 circuit starts the outdoor unit on
low−cooling speed, and the R−to−G−and−Y1 circuit starts the
furnace blower motor BLWM at low−cooling airflow which is the
true on−board CF (continuous fan) selection as shown in Fig. 65.
The R−to−Y1−and−Y2 circuits start the outdoor unit on
high−cooling speed, and the R−to− G−and−Y/Y2 circuits start the
furnace blower motor BLWM at high−cooling airflow.
High−cooling airflow is based on the A/C (air conditioning)
selection shown in Fig. 64.
The electronic air cleaner terminal EAC−1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R−to−G−and−Y1 or R−to−
G−and−Y1−and−Y2 circuits are opened. The outdoor unit stops,
and the furnace blower BLWM and electronic air cleaner terminal
EAC−
1 will remain energized for an additional 90 sec. Jumper Y1
to DHUM to reduce the cooling off−delay to 5 sec. See Fig. 38.
4. Dehumidification Mode
See Fig. 38 and 39 for thermostat connections.
The dehumidification output, D or DHUM on the Thermo-
stat should be connected to the furnace control thermostat
terminal DHUM. When there is a dehumidify demand, the
DHUM input is activated, which means 24 vac signal is re-
moved from the DHUM input terminal. In other words, the
DHUM input logic is reversed. The DHUM input is turned
ON when no dehumidify demand exists. Once 24 vac is de-
tected by the furnace control on the DHUM input, the fur-
nace control dehumidification capability is activated. If the
DHUM input is removed for more than 48 hours, the fur-
nace control reverts back to non−dehumidification mode.
The cooling operation described in item 3. above also ap-
plies to operation with a dehumidification thermostat. The
exceptions are listed below:
a. Low cooling−When the R−to−G−and−Y1 circuit is closed
and there is a demand for dehumidification, the furnace
blower motor BLWM will drop the blower airflow to 86
percent of low−cooling airflow which is the true on−board
CF (continuous fan) selection as shown in Fig. 64.
b. High cooling−When the R−to−G−and Y/Y2 circuit is
closed and there is a demand for dehumidification, the fur-
nace blower motor BLWM will drop the blower airflow to
86 percent of high−cooling airflow. High−cooling airflow
is based on the A/C (air conditioning) selection shown in
Fig. 64.
c. Cooling off−delay−When the “call for cooling” is satisfied
and there is a demand for dehumidification, the cooling
blower−off delay is decreased from 90 sec to 5 sec.
5. Super−Dehumidify Mode
Super−Dehumidify mode can only be entered if the furnace
control is in the Thermidistat mode and there is a demand
for dehumidification. The cooling operation described in
item 3 above also applies to operation with a dehumidifica-
tion thermostat. The exceptions are listed below:
a. When the R−to−Y1 circuit is closed, R−to−G circuit is
open, and there is a demand for dehumidification, the fur-
nace blower motor BLWM will drop the blower airflow to
65 percent of low−cooling airflow for a maximum of 10
minutes each cooling cycle or until the R−to−G circuit
closes or the demand for dehumidification is satisfied.
Low−cooling airflow is the true on−board CF (continuous
fan) selection as shown in Fig. 64.
b. When the R−to−Y/Y2 circuit is closed, R−to−G circuit is
open, and there is a demand for dehumidification, the fur-
nace blower motor BLWM will drop the blower airflow to
65 percent of high−cooling airflow for a maximum of 10
minutes each cooling cycle or until the R−to−G circuit
closes or the demand for dehumidification is satisfied.
986TB
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